feat: speed up unmarshaller with common signature trees

[bdraco]

This is ~4%-6% speed up (there is some margin of error)

[codecov]

Codecov Report

Base: 81.39% // Head: 81.18% // Decreases project coverage by -0.20% ⚠️

Coverage data is based on head (2201659) compared to base (3eb123b).
Patch coverage: 93.33% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #120      +/-   ##
==========================================
- Coverage   81.39%   81.18%   -0.21%     
==========================================
  Files          27       27              
  Lines        3015     3024       +9     
  Branches      582      582              
==========================================
+ Hits         2454     2455       +1     
- Misses        347      353       +6     
- Partials      214      216       +2     

Impacted Files	Coverage Δ
src/dbus_fast/__version__.py	0.00% <0.00%> (ø)
src/dbus_fast/_private/unmarshaller.py	94.50% <100.00%> (+0.18%)	⬆️
src/dbus_fast/aio/message_reader.py	95.45% <0.00%> (-4.55%)	⬇️
src/dbus_fast/glib/message_bus.py	81.14% <0.00%> (-2.05%)	⬇️
src/dbus_fast/signature.py	56.76% <0.00%> (-0.44%)	⬇️
src/dbus_fast/message_bus.py	70.81% <0.00%> (-0.19%)	⬇️

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[bdraco]

Production testing 👍